Fixation screw, graft ligament anchor assembly, and method for securing a graft ligament in a bone tunnel

ABSTRACT

A fixation screw, graft ligament anchor assembly, and method for fastening a graft ligament in a bone tunnel. The screw comprises an elongated shank having a distal end and a proximal end, and a central axis extending from the distal end to the proximal end. Screw threads are disposed on the shank and extend from the distal end to the proximal end. The proximal end defines an end plane disposed transversely to the axis and at an angle thereto other than a normal angle.

FIELD OF THE INVENTION

This invention relates to medical apparatus and methods in general, andmore particularly to apparatus and methods for reconstructing ligaments.

BACKGROUND OF THE INVENTION

Ligaments are tough bands of tissue which serve to connect the articularextremities of bones, or to support and/or retain organs in place withinthe body. Ligaments are typically composed of coarse bundles of densewhite fibrous tissue which are disposed in a parallel or closelyinterlaced manner, with the fibrous tissue being pliant and flexible butnot significantly extensible.

In many cases ligaments are torn or ruptured as a result of accidents.Various procedures have been developed to repair or replace such damagedligaments.

For example, in the human knee, the anterior and posterior cruciateligaments (i.e., the “ACL” and “PCL”) extend between the top end of thetibia and the bottom end of the femur. The ACL and PCL cooperate,together with other ligaments and soft tissue, to provide both staticand dynamic stability to the knee. Often, the anterior cruciate ligament(i.e., the ACL) is ruptured or torn as a result of, for example, asports-related injury. Consequently, various surgical procedures havebeen developed for reconstructing the ACL so as to restore substantiallynormal function to the knee.

In many instances, the ACL may be reconstructed by replacing theruptured ACL with a graft ligament. More particularly, in suchprocedures, bone tunnels are generally formed in the top end of thetibia and the bottom end of the femur, with one end of the graftligament being positioned in the femoral tunnel and the other end of thegraft ligament being positioned in the tibial tunnel. The two ends ofthe graft ligament are anchored in place in various ways well known inthe art so that the graft ligament extends between the bottom end of thefemur and the top end of the tibia in substantially the same way, andwith substantially the same function, as the original ACL. This graftligament then cooperates with the surrounding anatomical structures soas to restore substantially normal function to the knee.

In some circumstances, the graft ligament may be a ligament or tendonwhich is harvested from elsewhere in the patient; in othercircumstances, the graft ligament may be a synthetic device. For thepurposes of the present invention, all of the foregoing are collectivelyreferred to as a “graft ligament”.

It has been found that in securing graft tendons to tibias, because ofthe surface configuration of the tibia bone it often is necessary toadvance a fixation screw well into a bone tunnel in the tibia, often sofar that for one side of the screw to be substantially flush with thebone tunnel opening, the other side of the screw will have advanced pastthe outer dense hard cortical bone and entered the inner and softercancellous bone.

It has further been found that to refrain from advancing the fixationscrew to the aforementioned location (that is, to leave a portion of thescrew in cortical bone all around the screw) requires that a proximalportion of the screw remain outside the bone tunnel and project from thetibia.

Thus, there is a need for a fixation screw, graft ligament anchorassembly and method which affords full advancement of a fixation screw,but at the same time permits the screw to be engaged all around in thecortical portion of the tibia or other bone.

OBJECTS OF THE INVENTION

An object of the invention is to provide a fixation screw configured fordisposition in cortical bone portions, so as to strengthen the retentionof the screw in the bone.

Another object of the invention is to provide a fixation screw which,when the screw is fully implanted, substantially conforms to asurrounding bone surface at a proximal end of the screw.

A further object of the invention is to provide a graft ligament anchorassembly for improved retention in a bone, such as a tibia, and which inoperative position conforms to a surrounding bone surface.

A still further object is to provide a method for securing a graftligament in a bone tunnel so as to improve retention of the graftligament in the bone, and so as to provide for conformance of a graftligament anchor and fixation screw to a surface of surrounding hone.

SUMMARY OF THE INVENTION

With the above and other objects in view, as will hereinafter appear,there is provided a fixation screw for fastening a graft ligament in abone tunnel. The screw comprises an elongated shank having a distal endand a proximal end, and a central axis extending from the distal end tothe proximal end. Screw threads are disposed on the shank and extendfrom the distal end to the proximal end. The proximal end defines an endplane disposed transversely to the axis and at an angle thereto otherthan a normal angle.

In accordance with a further feature of the invention there is provideda fixation screw comprising an elongated shank having a generallyconically-shaped distal end portion, a proximal end, and a central axisextending from the distal end portion to the proximal end. Screw threadsare disposed on the shank and extend from the distal end portion to theproximal end. The proximal end comprises a generally planar end surfacedisposed transversely to the axis and at an angle thereto other than anormal angle.

In accordance with a further feature of the invention, there is provideda fixation screw for fastening a graft ligament in a bone tunnel. Thescrew comprises an elongated shank having a generally conically-shapeddistal end portion, a proximal end, and a central axis extending fromthe distal end portion to the proximal end. Screw threads are disposedon the shank, and extend from the distal end portion to the proximalend. The proximal end comprises a generally planar end surface disposedtransversely to the axis and at an angle thereto other than a normalangle, and appropriate for positioning the end surface as generally acontinuation of surrounding hone surface of a body in which the graftligament is fastened.

In accordance with a further feature of the invention, there is provideda graft ligament anchor assembly comprising a tubular body having a boretherethrough, and proximal and distal ends. The tubular body is adaptedfor placement in a bone tunnel proximate an opening thereof in a bonesurface. The tubular body comprises a deferrable wall and defines, atleast in part, a chamber for receiving a graft ligament therein. Afixation screw is provided for insertion into the tubular body axiallyof the tubular body, for impinging upon the deferrable wall so as topress the deformable wall, and hence the graft ligament received in thechamber, toward a wall of the bore, to fix the graft ligament in thebone tunnel. The screw comprises an elongated shank having a generallyconically-shaped distal end portion, a proximal end, and a central axisextending from the distal end portion to the proximal end. Screw threadsare disposed on the shank and extend from the distal end portion to theproximal end. The proximal end comprises a generally planar end surfacedisposed transversely to the axis and at an angle thereto other than anormal angle, and appropriate for positioning as generally acontinuation of surrounding bone surface of a body in which the graftligament is fastened.

In accordance with a still further feature of the invention, there isprovided a method for securing a graft ligament in a bone tunnel havingan end opening in a bone surface, a free end of the graft ligamentextending out of the bone tunnel end opening. The method comprises thesteps of providing a fixation screw for insertion into the bone tunneladjacent the graft ligament for impinging upon the graft ligament and awall of the bone tunnel to fix the graft ligament in the bone tunnel.The screw comprises an elongated shank having a generallyconically-shaped distal end portion, a proximal end, and a central axisextending from the distal end portion to the proximal end. Screw threadsare disposed on the shank and extend from the distal end portion to theproximal end. The proximal end comprises a generally planar end surfacedisposed transversely to the axis and at an angle thereto other than anormal angle, and appropriate for positioning as generally acontinuation of surrounding portions of the bone surface. The methodfurther comprises the steps of pulling the graft ligament taut,inserting the screw into the bone tunnel and advancing the screw thereinto threadedly engage the graft ligament and a wall of the bone tunnel tofix the graft ligament in the bone tunnel, and turning the screw untilthe shank proximal end surface thereof is substantially a continuationof the surrounding bone surface.

In accordance with another feature of the invention, there is provided amethod for securing a graft ligament in a bone tunnel having an endopening in a bone surface, a free end of the graft ligament extendingout of the hone tunnel end opening. The method comprises the step ofproviding a graft ligament anchor comprising a tubular body having abore therethrough and proximal and distal ends, the tubular bodycomprising a deformable wall and defining at least in part a chamber,and a fixation screw. The screw comprises an elongated shank having agenerally conically-shaped distal end portion, a proximal end, and acentral axis extending from the distal end portion to the proximal end.Screw threads are disposed on the shank and extend from the distal endportion to the proximal end. The proximal end comprises a generallyplanar end surface disposed transversely to the axis and at an anglethereto other than a normal angle, and appropriate for positioning asgenerally a continuation of surrounding portions of the bone surface.The method includes the further steps of extending the graft ligamentfree end through the chamber, placing the tubular body in the endopening and in the bone tunnel, pulling the graft ligament taut,inserting the screw into the tubular body and advancing the screwtherein to press the deformable wall, and hence the graft ligamentreceived in the chamber, toward the wall of the bore, to fix the graftligament in the bone tunnels and turning the screw until the proximalend surface thereof is substantially a continuation of the bone surfacetherearound.

The above and other features of the invention, including various noveldetails of construction and combinations of parts and method steps willnow be more particularly described with reference to the accompanyingdrawings and pointed out in the claims. It will be understood that theparticular devices and method steps embodying the invention are shown byway of illustration only and not as limitations of the invention. Theprinciples and features of this invention may be employed in various andnumerous embodiments without departing from the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which are tobe considered together with the accompanying drawings wherein likenumbers refer to like parts, and further wherein:

FIG. 1 is a perspective view of one form, of a fixation screw forfastening a graft ligament in a bone tunnel, illustrative of anembodiment of the invention;

FIG. 2 is a side elevational view of an alternative embodiment offixation screw;

FIG. 3 is a diagrammatic illustration of the screw of FIG. 1 inoperation;

FIG. 4 is a diagrammatic illustration of a graft ligament anchorassembly including the screw of FIG. 1 and illustrating an anchorassembly in operation; and

FIG. 5 is a diagrammatic illustration of still another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, it will be seen that an illustrative fixation screw10 includes an elongated shank 12 having a distal end portion 14, whichmay be generally conically-shaped, as shown in FIG. 1, and have agenerally pointed distal end 16. The shank 12 is further provided with aproximal end 18 defining an end plane b-b. A central axis a-a extendsfrom the distal end 16 to the proximal end 18. The plane b-b is disposedtransversely to the axis a-a and at an angle c thereto, the angle cbeing other than a normal angle, and preferably of about 40°-55°. Theproximal end 18 may comprise a generally planar surface 22, asillustrated in FIG. 1. Screw threads 28 are disposed on the shank 12 andextend from the distal end 16 to the proximal end 18.

Referring to FIG. 2, it will be seen that the fixation screw 10 may beof tubular structure and provided with apertures 24 extending throughsidewalls 26 thereof, facilitating ingrowth of bone to further securethe screw in place over time. Further, as shown in FIG. 2, the distalend portion 14 of the screw 10 may be other than conical, such asgenerally cylindrical, and the distal end 16 of the screw 10 may beother than pointed, such as defining a plane normal to the axis a-a.

in FIG. 3, there is illustrated a manner in which the fixation screw 10of FIG. 1 or FIG. 2 may be used to secure a graft ligament 30 in a bonetunnel 32 having an end opening 34 in a bone surface 36. In FIG. 3, thebones shown for illustrative purposes are major bones of a knee joint,including a femur 38 and tibia 40. The invention presumes that one end42 of the ligament 30 has been secured in the femur in accordance withknown methods and that another end portion 44 extends from the endopening 34.

In the method illustrated in FIG. 3, an operator pulls the ligament 30taut by manipulation of the exposed ligament end portion 44. The screw10 is then inserted into the bone tunnel 32, by way of the end opening34. The screw 10 is advanced into the bone tunnel 32, threadedlyengaging the ligament 30 and a wall 46 of the bone tunnel 32, to securethe ligament 30 in the bone tunnel 32. As the screw 10 advances tonearly full insertion, the screw is turned until the shank proximal endsurface 22 is disposed so as to be substantially flush with, and formsubstantially a continuation of, the surrounding bone surface 36.

Thus, threaded portions of the screw 10 are engaged throughout 360° withcortical portions 48 of the tibia 40, or other selected bone, tosecurely retain the screw in place. With the screw 10 in place, theexposed ligament end portions 44 may be snipped off along lines 50,shown in FIG. 3 (the “snipped off” portions of ligament end portions 44are shown in phantom in FIG. 3). As noted above, when the embodiment offixation screw shown in FIG. 2 is used, over time material from the bonewall 46 will migrate through the apertures 24, to further lock the screwin place.

In FIG. 4, there is shown a graft ligament anchor 60 in a tibia 40. Theanchor 60 includes the screw 10, as described hereinabove, and a tubularbody 62 having a bore 64 therethrough and having distal and proximalends 66, 68. The tubular body 62 is adapted for placement in the bonetunnel 32 proximate the end opening 34 thereof in the bone surface 36. Adeformable wall 70 is disposed in the tubular body, defining at least inpart a chamber 72 for receiving the graft ligament 30 therein.

In the anchor assembly 60 shown in FIG. 4, the tubular body 62 itselfforms a deformable wall 70. In pending prior U.S. patent applicationSer. No. 09/248,523, filed Feb. 9, 1999 by Joseph H. Sklar for GRAFTLIGAMENT ANCHOR AND METHOD FOR ATTACHING A GRAFT LIGAMENT TO A BONE,which pending prior patent application is hereby incorporated herein byreference, there are disclosed several ligament anchor assemblies havingtubular bodies with alternative arrangements of deformable walls andappropriate for use in the anchor assembly presented herein.

In use of the graft ligament anchor assembly, the ligament end portions44 are extended through the tubular body chamber 72 by an operator. Thetubular body 62 is inserted in the end opening 34 of the bone tunnel 32.The ligament 30 is pulled taut by the operator. The fixation screw 10 isthen inserted into the tubular body 62 and advanced to press the graftligament 30 and deformable wall 70 toward the wall 46 of the bone tunnel32, to fix the ligament to the bone tunnel wall 46. As the proximal end18 of the screw 10 draws near the bone surface 36, the screw 10 isturned until the screw proximal end surface 22 is disposed so as to beflush with, and substantially a continuation of, the bone surface 36therearound.

The tubular body 62 and the ligament end portions 44 may then be snippedoff to provide a relatively smooth surface in the area of the closedopening 34 (the “snipped off” portions of tubular body 62 and theligament end portions 44 are shown in phantom in FIG. 4).

In the embodiment shown in FIG. 4, the threads 20 of the screw 10 do notdirectly engage the cortical bone 48; however, the threads 20 force thetubular body 62 into engagement with the cortical bone 48, providingstronger fixation than if similarly engaged with a cancellous portion 74of the bone 40.

There is thus provided an improved fixation screw, graft ligament anchorassembly and methods for fixing ligaments in bone tunnels.

In the aforementioned U.S. patent application Ser. No. 09/248,523, whichpatent application has already been incorporated herein by reference,there are also disclosed bone tunnel liners for lining the wall of abone tunnel prior to securing a graft ligament therein.

Looking now at FIG. 5, there is shown a bone tunnel liner 100 which maybe positioned within a bone tunnel 32 of a bone 40. Bone tunnel liner100 includes a central bore 102 extending from its distal end 104 to itsproximal end 106. The outer surface of bone tunnel liner 100 includesscrew threads 108 and preferably includes openings 110. In use, bonetunnel liner 100 is positioned in bone tunnel 32 in bone 40, the graftligament's end portions are extended through chambers 72 of tubular body62, tubular body 62 is inserted into bone tunnel liner 100, and fixationscrew 10 is inserted into the central bore of tubular body 62 andadvanced distally so as to press the tubular body's deferrable walls,and hence the graft ligament, toward bone tunnel liner 100, whereby tosecure the graft ligament in the bone tunnel.

In accordance with the present invention, the proximal end 106 of bonetunnel liner 100 is preferably formed with an end surface which is setat an angle to the longitudinal axis of the bone tunnel liner, wherebythe proximal end of the bone tunnel liner may be disposed flush with,and substantially a continuation of, the bone surface 36 therearound.

It is to be understood that the present invention is by no means limitedto the particular construction and method steps herein disclosed and/orshown in the drawings, but also comprises any modification or equivalentwithin the scope of the claims. For example, it will be apparent thatthe particular inclination of the proximal end plane to the shankcentral axis is selected to match the bone surface 36. The angle isdetermined by the application site morphology.

1.-24. (canceled)
 25. A bone tunnel liner for lining the wall of a bonetunnel which is to have a graft ligament fastened therein, said bonetunnel liner comprising; a tube having a distal end and a proximal end,and a central axis extending from said distal end to said proximal end;and screw threads disposed on said tube and extending from said distalend to said proximal end; wherein said proximal end defines an end planedisposed transversely to the central axis and at an angle thereto otherthan a normal angle.